Answer
The equation is:


Mars take 322 days more than Earth to orbit the sun
Explanation:
- Earth takes 365 days to orbit the sun
- Mars takes 687 days to orbit the sun
The equation to find how many more days mars take than earth to orbit the sun can be write as:

Where:
D: Days mars take than earth to orbit the sun
M: Days Mars takes to orbit the sun
E: Days Earth takes to orbit the sun

Mars take 322 days more than Earth to orbit the sun